The invention covers a metal smelting plant with a treatment stand to regulate the analysis or various components comprising metal smelts, particularly for desulphurization of liquid pig iron or liquid unrefined steel, such treatment stand being equipped to add desulphurizing and/or carburizing agents, alloying agents; to inject reactive or inert gases; to evacuate gases and extract slag; and being equipped with dollies and/or cranes, their tracks being installed before the smelting furnaces in the charging hall.
Desulphurization of pig iron in a steel mill is done in lieu of desulphurization after tapping from the blast furnace or in lieu of desulphurization in a mobile receptacle (torpedo ladle truck) between blast furnace and steel mill. Desulphurization in the steel mill is intended to lower the initial sulphur contents of e.g. 0.035% to 0.045% sulphur in order to create favorable conditions for the blasting process, after which the final sulphur contents of the finished steel are so low that higher quality of steel, such as high-duty steel, steel for the manufacture of electric plate, roller bearing steel and the like may be produced. Desulphurization of crude iron after the blasting process is used to vary the percentage of several components in the iron in order to influence casting and cooling conditions as well as material properties, and also the properties of the finished material.
The applicable metallurgic refining and/or alloying methods for the smelting of metals and metal alloys determine the ultimate properties of the material being worked or the material flux in the metal smelting plant. The desired properties of the material flux, in turn, determine the planning of the metal smelting plant.
If the metal smelting plant consists of a steel mill, the material being processed goes from the pig iron supply (blast furnace or pig iron mixer) and from the junk yard (solid metal) to the charging hall in front of the smelting furnaces. The liquid metal (steel) tapped from the smelting furnaces (steel mill converters) is either transported through the charging hall into the casting hall where it is cast into upright molds, or it is transported to strand-casting facilities bordering on the smelting furnace hall.
In accordance with a familiar proposal (technical magazine "Steel and Iron" issue of Oct. 26th, 1972, pages 1088/1089) pig iron may be desulphurized in torpedo ladles outside the steel mill in a treatment stand between blast furnace and steel mill. Placing such treatment stand inside the steel mill, however, will result in shorter transport distances and consequently decreased heat loss in the liquid metal. With a treatment stand inside the steel mill, the temperatures of the liquid metal before and after desulphurization and/or dephosphorization and/or desilicification may be maintained more closely.
In a metal smelting plant where steel or copper or other non-ferrous metals are smelted, the main transportation route for liquid pig iron, solid carburizing materials, additives and and casting metal occupies an area in the charging and/or casting hall, which is not to be encumbered by additional means of transportation. If, however, the liquid crude metal or the casting metal are to be subjected to special treatment inside the smelting plant, additional means and routes of transportation cannot be avoided. It is known to perform these specific individual treatment stages successively in several locations inside the metal smelting plant in order to avoid the difficulties mentioned.
Another lack in the present status of technology lies with the treatment stand itself. The familiar treatment stands arranged outside the metal smelting plant and the various parts of equipment distributed in various locations in the steel mill for the treatment of liquid crude metal are either usable for smaller openings of the treatment vessel only or cannot be used for tilting vessels in the shape of ladles. A particular lack in the familiar treatment equipment lies in the insufficient removal of waste gases which escape during the treatment process. Another deficiency is the mutual interference of the individual parts of the equipment.
The object of the present invention is to arrange the treatment stand within a metal smelting plant in a location where the main material line of the metal smelting plant is never disturbed nor subjected to additional burden by the delivery and removal of the liquid crude metal to be treated from the area adjacent the main processing line.
One of the tasks to be solved by the invention is to improve upon a construction of the treatment stand for introducing additives, for example, to eliminate the disadvantages mentioned, and thus to increase the capacity of the treatment stand.
The invention solves this by arranging the treatment stand in the halls or rooms bordering on the charging hall and/or smelting furnace hall, level with the mill floor or on an elevated platform and connected via at least one transportation branch line to the main processing transportation line running in the charging hall, smelting furnace hall or towards the casting stand. The main material being treated of the metal smelting plant is thus neither disturbed nor subjected to any unnecessary additional burden. Material flux for pig iron production and for desulphurization does not occupy the same means for transportation, nor do their paths cross. This guarantees smooth operation, and delays resulting in temperature losses are avoided. Generally, the treatment stand is arranged on the mill floor. This arrangement meets the requirements of preliminary treatment of the liquid crude metal before its finishing treatment in the smelting furnaces (steel mill converters). If the floor space of the metal smelting plant is insufficient, the treatment stand may favorably be arranged, e.g. in a steel mill, on a raised platform, e.g. above the mixing hall. In accordance with the invention, the main material flux line is not disturbed even if the treatment stand is arranged in the area of the casting platform of a strand casting plant or on the casting platform of the strand casting plant.
Anothr possibility of location in a steel mill is to arrange the treatment stand inside the casting hall for the purpose of desulphurization of pig iron, connected to the main material processing line from the smelting furnace hall to the casting hall.
In case the metal smelting plant is a steel mill, the branch transportation line may consist of a single rail, on which a cart travels back and forth between treatment stand and the respective means of transportation which carries out all transport within the main material flux or processing line.
In this sense provision is made in the steel mill for at least one rail running at right angles with the travel course of the pig iron crane in the main line, a ladle truck running on such rail which is arranged on the mill floor from the charging hall to the mixing hall and/or from the smelting furnace hall to the casting hall. This rail is the simplest and shortest branch line from the main transport route for the material being processed.
Furthermore a tilting mechanism with a gear for the ladle is arranged on the truck which is movable in the direction of movement of the main line, and a depot or storage area is provided for a slag receptacle, and the pouring snout of the ladle faces the slag receptacle. Such ladle truck permits the removal of slag from the ladle inside or outside the treatment stand.
Of particular importance are the following pieces of equipment provided for the treatment stand:
A track for a travelling desulphurization setup is arranged above the ladle truck in the treatment stand. The mobility of the desulphurization setup works two ways: a single desulphurization setup may be moved out of the treatment stand so that other equipment, e.g. gas evacuation equipment, may be brought into position. Secondly, the mobility is of particular advantage if operation takes place in accordance with the blastlance method or the magnesium coke bell method in order to accommodate placement of this special equipment.
Each of these methods require the insertion of an object into the treatment ladle. The invention provides the space necessary for this even if space is very limited. The bell for coke and magnesium and/or the blast-lance devices can also have a mobile arrangement.
Another characteristic of the invention is that the track for the travelling desulphurization equipment runs at right angles with the course of the ladle truck.
The principle of the invention with respect to the design of a treatment stand may also be directed towards high capacity for large quantities of pig iron to be desulphurized: to this end, several rails running at right angles with the course of the crude iron crane, for one ladle truck each, are provided as well as one track for at least one travelling desulphurization plant covering several treatment stands. It is particularly favorable to operate one single travelling desulphurization plant in chronological succession to each of the ladles in the treatment stand.
The invention further refers to the design of the travelling desulphurization plant:
The carriage of the travelling desulphurization plant includes a provision for an agitator which may be raised or lowered, with its rotary transmission or drive, for a ladle lid to be raised or lowered, with adapter for an evacuation device and an adapter for a feed pipe, whereby both adapters in operating position for the desulphurization automatically form a connection with their respective stationary equipment.
After removing the desulphurization equipment to which the ladle lid to be raised or lowered is attached, further pieces of equipment characteristic of the invention may be brought into operating position: A gas evacuation hood, to be raised or lowered, is arranged above the travelling desulphurization plant; in its lowered position such hood covers the tilting ladle and the slag receptacle and it has an opening permitting the movement of a slag removal crutch, which opening, in this position, is approximately opposite the ladle pouring snout. This makes it feasible to catch and remove the waste gases escaping during slag removal even while the ladle is tilted.
A slag removal device travels on a track running perpendicular with the tilting direction of the ladle, and the slag removal crutch of such device can be moved back and forth in tilting direction of the ladle. The mobility of the slag removal device and the feeding movements permit superposed movements in order to sweep the surface of the treated liquid metal.
In further improvement the track for the slag removal device is extended in at least one direction past the treatment stand to provide a storage station. Furthermore the track for at least one slag removal device covers several treatment locations of one or several treatment stands. Consequently, one single slag removal device is sufficient for one treatment stand with several treatment locations.